On January 23, 2007, two days after the Bears won the NFC Championship Game, Johnson was forced to appear in Circuit court to request permission to leave the State of Illinois to travel to Miami, Florida to play in Super Bowl XLI stemming from an arrest on gun charges late in 2006.[3] The request was granted, and he played in the game, recording four tackles, assisting on another, and getting a half-sack.[4] On May 16, 2007, Johnson met with NFL commissioner Roger Goodell to determine punishment for his off-the-field transgressions,[5] with Goodell eventually imposing an eight-game suspension, with the possibility of a reduction to six games if Johnson followed certain requirements for violating the NFL player conduct policy.

On June 25, 2007, after another run in with the law, the Chicago Bears waived Johnson, ending his three-year tenure with the team.[6]

After being released from the Bears, Jerry Jones showed interest in signing Johnson.[7] The two shortly came to terms, though Johnson was forced to miss eight games because of his suspension.[8] He returned to the field on November 11, 2007 during a game against the New York Giants. In that game, Johnson recorded three solo tackles, and a single sack.

He didn't perform as well as expected while playing nose tackle in a 3-4 defense, instead of defensive tackle in a 4-3 scheme, additionally Jay Ratliff had a break-out year at nose tackle. In 2008, he played through a sprained ankle in a reserve role. He wasn't re-signed at the end of the year.

Johnson signed with Cincinnati Bengals on April 7, 2009.[9] As an unrestricted free agent, Johnson signed with the Bengals to a 4-year deal on March 8, 2010. His contract was terminated with the Bengals on August 16, 2011.

After retiring from pro-football, Johnson attended Mesa Community College in Arizona to complete the requirements for a degree in sociology from the University of Washington.[10] He created a counseling program called 'Moving the Chains', which helps ex-offenders learn from their mistakes and avoid negative influences in their life.[10] Johnson commented on his legal problems, stating, "I got in a ton of trouble and I wasn't a bad guy. I had myself in too many uncontrolled environments."[10]

In November 2005, Johnson was arrested at the Excalibur nightclub in Chicago for possession of a handgun in his sport utility vehicle. Illinois law dictates that "It is unlawful to carry or possess any firearm in any vehicle or concealed on or about the person, except on one’s land or in one’s [home] or fixed place of business."[11] At the time, Illinois was the only US state that did not issue Concealed Carry Permits. Johnson pleaded guilty to a misdemeanor gun charge and was sentenced to 18 months probation and 40 hours of community service.[12] On February 12, 2006, Johnson, while still on probation, was charged with aggravated assault and resisting arrest after allegedly verbally threatening a police officer. Johnson was leaving the Level Nightclub on Chicago's Rush Street when the police officer was ticketing a limousine driver whom Johnson had hired. As Johnson allegedly put up a struggle, he was maced and subdued with the help of other police officers. The charges were eventually dropped.[13]

On December 14, 2006, Lake County police officers searched Johnson's home in Gurnee, Illinois, and allegedly discovered that he possessed six firearms, including two assault rifles. According to police reports, some of the guns were loaded and there were children in the house.[14] Although Johnson was at football practice during the search, his bodyguard William Posey was arrested from his house for alleged possession of marijuana. Johnson was charged with violation to probation and possessing unlicensed weapons. Bears coach Lovie Smith deactivated Johnson for the following game against the Tampa Bay Buccaneers based on this incident.[15]

On December 16, 2006, Johnson's best friend and bodyguard William Posey was killed in a shooting at the Ice Bar in Chicago's River North neighborhood. Posey was shot after he was allegedly involved in a fight around midnight. Posey was rushed to Northwestern Memorial Hospital, where he was pronounced dead at 1:30 a.m. Posey's assailant was not immediately apprehended.[16] However, on December 28, Chicago Police apprehended Michael Selvie, Posey's alleged assailant. Selvie, a "reputed gang member" has been implicated in over 30 other crimes. However, Selvie's defense attorney claimed that Selvie does not possess a firearm or any gang affiliations. On February 19, 2010, following a bench trial in the Circuit Court of Cook County, Michael Selvie was convicted of first degree murder. Selvie was later sentenced to 55 years in prison. His case is currently on appeal.

On December 22, 2006, Cook County Circuit Judge John J. Moran, Jr. (Skokie courthouse, Second District, Cook County, Illinois) placed Johnson on home confinement, preventing him from driving by himself or leaving the state of Illinois.[17] On December 30, 2006, Tank Johnson contacted Gurnee Police Department to file harassment charges.[18] Local youths left a toilet seat with a harassing message on his doorstep. Local news reported that the police did not disclose what the message on the toilet seat said.[19] On February 8, 2007, Johnson entered a guilty plea in Cook County's Courthouse in Skokie for violating his probation.[20] On February 17, 2007, Johnson's lawyer contested a Lake County Circuit Court to drop Johnson's unlicensed weapons charges. His attorney claimed that since Johnson is a resident of Arizona, he does not have to abide to gun registration laws of Illinois.[21] On March 15, 2007, Johnson was sentenced to a 120 days in Cook County Jail and fined $2,500 for violating his probation.[22] Johnson entered a plea of not guilty on 10 counts of possessing a weapon without the proper state-required ID.[23]

On April 30, 2007, Johnson pleaded guilty to a misdemeanor weapons charge as part of an arrangement with prosecutors that kept him from serving additional jail time. He was sentenced to 45 days in jail, which was served concurrently with a four-month sentence he was already serving in the Cook County Jail for violating his probation; to donate $2,500 to the Gurnee Police Department and $2,500 to the Gurnee Exchange Club's child abuse prevention program.[24] While he was in jail, many of his teammates and coaches, including Brian Urlacher, Rex Grossman, and Lovie Smith visited Johnson.[25] His release from jail on May 13, 2007 ended his legal problems from the December 2006 weapons incident.[26] The league ultimately suspended Johnson for half of the regular season on June 4, 2007.[27]

On June 22, 2007, Johnson was pulled over for speeding in Gilbert, Arizona. According to the police, he was stopped by after driving forty miles per hour in a twenty-five mile per hour zone. He was also suspected of driving while impaired "to the slightest degree", but was released without being booked or charged. The Bears waived Johnson a few days after hearing the news, as general manager Jerry Angelo stated that he had no room for error left.[28] The incident would prove to be the final straw in his already tense relationship with the Bears' organization. The Bears ultimately released Johnson on June 25, 2007.[29] Almost a week after Johnson was waived, the results from a blood test conducted on Johnson when he was pulled over confirmed his blood alcohol content was under the legal limit.[30]